The quid pro quo of blood pressure control and dementia
Authors: Joanne Ryan, Michael E Ernst
Journal: The Lancet Healthy Longevity (2023)

Hypertension affects an estimated 1·5 billion adults worldwide and is responsible for 7·6 million cardiovascular disease (CVD) and stroke deaths annually.1Arima H Barzi F Chalmers J Mortality patterns in hypertension.J Hypertens. 2011; 29: S3-S7Crossref PubMed Scopus (103) Google Scholar It is also linked to other age-related conditions. Midlife hypertension is a risk factor for dementia,2Livingston G Huntley J Sommerlad A et al.Dementia prevention, intervention, and care: 2020 report of the Lancet Commission.Lancet. 2020; 396: 413-446Summary Full Text Full Text PDF PubMed Scopus (3236) Google Scholar and emerging evidence suggests that improving blood pressure control can reduce mild cognitive impairment and, potentially, dementia.3Williamson JD Pajewski NM Auchus AP et al.Effect of intensive vs standard blood pressure control on probable dementia: a randomized clinical trial.JAMA. 2019; 321: 553-561Crossref PubMed Scopus (678) Google Scholar Hypertension also increases risk of disability, in part driven by its adverse effects on CVD and cognition.4Elias Mf Fau - Elias PK Elias PK. Blood pressure and disability: novus orsa.Hypertension. 2017; 50: 1006-1008Crossref Scopus (8) Google Scholar Public health initiatives over the last 40 years have yielded declines in hypertension prevalence in high-income countries, largely owing to improvements in lifestyle (eg, reductions in dietary salt5He FJ Li J Macgregor GA Effect of longer term modest salt reduction on blood pressure: Cochrane systematic review and meta-analysis of randomised trials.BMJ. 2013; 346f1325 Crossref PubMed Scopus (903) Google Scholar) and effective treatment with antihypertensives.6Zhou B Perel P Mensah GA-O Ezzati M Global epidemiology, health burden and effective interventions for elevated blood pressure and hypertension.Nat Rev Cardiol. 2021; 18: 785-802Crossref PubMed Scopus (296) Google Scholar Understanding the broad impact of hypertension reduction strategies is essential to shaping future public policy. Although studies have estimated mortality and life-years gained from hypertension interventions, the majority have focused on single outcomes without considering their downstream effect on age-related conditions, and their dynamic interplay with hypertension. In The Lancet Healthy Longevity, Yuntao Chen and colleagues7Chen Y Araghi M Bandosz P et al.Impact of hypertension prevalence trend on mortality and burdens of dementia and disability in England and Wales to 2060: a simulation modelling study.Lancet Healthy Longev. 2023; (published online Aug 10.)https://doi.org/10.1016/S2666-7568(23)00129-0Summary Full Text Full Text PDF Google Scholar take a comprehensive approach using nationally representative data from England and Wales collected between 2006 and 2017. They modelled three different hypertension prevalence scenarios for individuals aged 35–100 years, stratified by age and sex. The transition probabilities through ten health states were calculated, ranging from being without CVD or cognitive or functional impairment, to various combinations of these conditions, and death from CVD or non-CVD causes. The results estimated the impact of hypertension prevalence on the future burden of dementia and disability over 40 years, given current trends in demographics, disease incidence, and mortality. Not unexpectedly, the authors found that the major impact of varying hypertension prevalence is on life expectancy and healthy life expectancy. In the optimistic scenario, a 50% reduction in hypertension prevalence up to 2040, compared with the steady downward trend currently observed, would result in fewer deaths. Life expectancy at age 65 years would increase by 4·3 years from 2020 to 2060, and there would be an 8·1% increase in healthy life expectancy at age 65 years. In contrast, the impact of varying hypertension prevalence on dementia and disability was modest, with the decline in hypertension prevalence paradoxically leading to a small increase in dementia burden. This is because the expected reduction in incident CVD and CVD-related deaths due to better control of hypertension was counterbalanced by more individuals living to older ages. This quid pro quo, shifting the disease burden to other conditions, is seldom considered in studies investigating the public health impact of prevention strategies. The elegant analysis by Chen and colleagues7Chen Y Araghi M Bandosz P et al.Impact of hypertension prevalence trend on mortality and burdens of dementia and disability in England and Wales to 2060: a simulation modelling study.Lancet Healthy Longev. 2023; (published online Aug 10.)https://doi.org/10.1016/S2666-7568(23)00129-0Summary Full Text Full Text PDF Google Scholar reveals the complexity of the shifting chronic disease burden, not addressed in earlier studies in which the impact of preventive interventions were considered for a singular outcome. By surviving longer, more individuals become at risk of other age-related diseases. While that might appear to offset benefits of hypertension control, if the overall time spent with morbidity also decreases, then the net effect is a compression of, rather than an expansion of, morbidity. Reducing the amount of time individuals live with disease, and the associated burdens on the health system and society, is a primary goal of health organisations and government bodies worldwide. Collectively, the findings by Chen and colleagues draw attention to the ongoing need for comprehensive prevention strategies targeting not only the immediate condition of interest, but also other risk factors and their associated outcomes that are inextricably entwined. Some caveats should be considered in the current simulation study. Most notably, it assumes that population levels of risk factors affecting the incidence of these outcomes would follow the same trends observed over the past two decades. Reversing or slowing the rising trends in midlife obesity, for example, an established risk factor for CVD, dementia, and disability, would again shift the balance. In such simulation studies, burden is defined simplistically based on the number of cases of the disease. It does not consider how the true socioeconomic costs associated with these conditions could also change over time.8El-Hayek YH Wiley RE Khoury CP et al.Tip of the iceberg: assessing the global socioeconomic costs of Alzheimer's disease and related dementias and strategic implications for stakeholders.J Alzheimers Dis. 2019; 70: 323-341Crossref PubMed Scopus (115) Google Scholar Furthermore, with the considerable recent advances in treatments for early-stage Alzheimer's disease, which appear efficacious in slowing clinical progression, the future impact of dementia could be reduced.9Sims JR Zimmer JA Evans CD et al.Donanemab in early symptomatic Alzheimer disease: the TRAILBLAZER-ALZ 2 randomized clinical trial.JAMA. 2023; (published online July 17.)https://doi.org/10.1001/jama.2023.13239Crossref Google Scholar Finally, the simulation study was conducted in the UK, and one could anticipate similar findings in other high-income countries. However, the downward trend in hypertension control might not continue,10Flack JM Better implementation of what is known will reverse falling hypertension control rates: we know how to reverse falling hypertension rates.Hypertension. 2021; 78: 588-590Crossref PubMed Scopus (5) Google Scholar and new strategies could well be needed. Furthermore, the situation in low-income and middle-income countries, where hypertension rates continue to rise,6Zhou B Perel P Mensah GA-O Ezzati M Global epidemiology, health burden and effective interventions for elevated blood pressure and hypertension.Nat Rev Cardiol. 2021; 18: 785-802Crossref PubMed Scopus (296) Google Scholar is likely to be very different. Addressing the barriers to hypertension control in these settings is crucial. We declare no competing interests. Impact of hypertension prevalence trend on mortality and burdens of dementia and disability in England and Wales to 2060: a simulation modelling studyThe major future impact of alternative hypertension prevention strategies appears to be on future life expectancy. The salutary effect of lower population blood pressure distribution on incidence of dementia and disability might not offset expansion of the susceptible population due to reduced mortality. Full-Text PDF Open Access